Biomedical subjects

X Gai

Publications and source records attributed to X Gai.

8 recordsLinked to original sources

PubMed2001

Palladium catalysed 3-component cascade synthesis of bis(2-arylallyl) tertiary amines from aryl iodides, allene and primary amines.

A 3-component cascade synthesis of bis(2-arylallyl) tertiary amines from aryl iodide, allene and primary aliphatic amines is described; chiral amines give analogous products with no detectable racemisation; mixtures of two different aryl iodides can be utilised to give the mixed tertiary amines as the sole, or major, product; the reaction is sensitive to stereoelectronic effects which lead to mono(2-arylallyl) secondary amines.

Journal Article↗

PubMed2001

Targeting of the yeast Ty5 retrotransposon to silent chromatin is mediated by interactions between integrase and Sir4p.

The Ty5 retrotransposons of Saccharomyces cerevisiae integrate preferentially into regions of silent chromatin at the telomeres and silent mating loci (HMR and HML). We define a Ty5-encoded targeting domain that spans 6 amino acid residues near the C terminus of integrase (LXSSXP). The targeting domain establishes silent chromatin when it is tethered to a weakened HMR-E silencer, and it disrupts telomeric silencing when it is overexpressed. As determined by both yeast two-hybrid and in vitro binding assays, the targeting domain interacts with the C terminus of Sir4p, a structural component of silent chromatin. This interaction is abrogated by mutations in the targeting domain that disrupt integration into silent chromatin, suggesting that recognition of Sir4p by the targeting domain is the primary determinant in Ty5 target specificity.

Amino Acid Motifs↗

PubMed2001

Preferential acetazolamide-induced vasodilation based on vessel size and organ: confirmation of peripheral vasodilation with use of colored microspheres.

When carbonic anhydrase activity decreases, the regional blood flow (rBF) in organs increases as hypercapnia develops. However, the effects of acetazolamide (AZ)-induced vasodilation have not been estimated with respect to vessel size and organs. The aim of this study was to determine the diameter of the capillaries in various organs that respond to inhibition of carbonic anhydrase activity by AZ. White rabbits were anesthetized with urethane and ketamine and infused with AZ. While the systolic blood pressure (SBP), pH, hemoglobin concentration, and base excess did not change, the partial pressure of arterial oxygen (PaO2) increased significantly and the partial pressure of arterial carbon dioxide (PaCO2) decreased significantly with AZ. The rBF was calculated by using 3 different sizes (15, 25, and 50 microm) of colored microspheres (CM). The rBF measured with 15 microm CM in the brain, kidneys, and liver increased in response to AZ, and the rBF in these organs was different with the different sizes of CM. However, the rBF calculated by using the different sizes of CM in the stomach and abdominal muscle did not change after the administration of AZ. The AZ-induced vasodilation occurred in all sizes of vessels in the liver, in the small and medium-sized vessels in kidneys, and in the larger capillaries in the brain.

Abdominal Muscles↗

PubMed2000

Gene discovery using the maize genome database ZmDB.

Zea mays DataBase (ZmDB) is a repository and analysis tool for sequence, expression and phenotype data of the major crop plant maize. The data accessible in ZmDB are mostly generated in a large collaborative project of maize gene discovery, sequencing and phenotypic analysis using a transposon tagging strategy and expressed sequence tag (EST) sequencing. ESTs constitute most of the current content. Database search tools, convenient links to external databases, and novel sequence analysis programs for spliced alignment are provided and together serve as an efficient protocol for gene discovery by sequence inspection. ZmDB can be accessed at http://zmdb. iastate.edu. ZmDB also provides web-based ordering of materials generated in the project, including EST and genomic DNA clones, seeds of mutant plants and microarrays of amplified EST and genomic DNA sequences.

Amino Acid Sequence↗

PubMed1998

A single amino acid change in the yeast retrotransposon Ty5 abolishes targeting to silent chromatin.

Many retrotransposons and retroviruses are thought to select integration sites through interactions with specific chromosomal proteins. In yeast, the Ty5 retrotransposon integrates preferentially with regions bound by silent chromatin, namely the telomeres and the HMR and HML mating loci. A Ty5 mutant (M3) was identified with an approximately 20-fold decrease in targeted integration as measured by a plasmid-based targeting assay. Often chromosomal insertions generated by M3, none were located at the telomeres or silent mating loci. A single amino acid change at the boundary of integrase and reverse transcriptase is responsible for the mutant phenotype. We predict that this mutation lies within a targeting domain that mediates Ty5 target choice by interacting with a component of silent chromatin.

Amino Acid Sequence↗

PubMed1996

[Clinical analysis of surgical treatment for 86 patients with localized small-cell lung cancer].

To assess the value of surgical treatment followed by adjuvant chemotherapy for localized small-cell lung cancer (SCLC), the results of treatment in 86 SCLC patients since 1990 were reviewed. Of 86 patients, 19 patients received pneumonectomy, 53 lobectomy, 6 wedge resection and 8 segmental resection. Postoperative pathologic staging revealed 24 in stage I, 36 in stage II, and 26 in stage III. Postoperative adjuvant chemotherapy was given in 78 patients. Until the latest follow-up, 28 patients remained alive and 58 patients died. The 5-year survival rate of the 86 patients was 37%. The survival of patients in stage I was better than that of patients in stage II (P = 0.018) and stage III (P = 0.021), but the survival of patients in stage II was not significantly different from that of patients in stage III (P = 0.234). In summary, surgical treatment followed by chemotherapy improves significantly the survival of patients with localized SCLC. TNM staging is of prognostic importance.

Carcinoma, Small Cell↗

PubMed1995

CCAAT-box contributions to human thymidine kinase mRNA expression.

In order to examine the role of two inverted CCAAT boxes near the start of transcription of the human thymidine kinase (TK) gene, a series of constructs were prepared in which one or both CCAAT boxes were deleted or mutated. These altered promoters (1.2 kb of 5'-flanking sequence) were used to express a TK minigene containing the first two exons and introns followed by the remainder of the cDNA. RNA blots were prepared from stable cell lines of ts13 cells containing these constructs under three conditions: 1) serum deprived cells, 2) serum stimulated cells, and 3) cells that had been stimulated with serum, but were arrested in the G1 phase of the cell cycle by the temperature sensitive mutation carried by these cells. TK mRNA expression from each construct was suppressed by the temperature sensitive block to cell cycle progression. Measurement of protein expression from the various altered TK promoters indicated that both CCAAT boxes contribute to promoter strength. These experiments also suggested that the two CCAAT boxes were not equivalent and that the distal CCAAT could substitute for the proximal CCAAT, but the converse was not true.

Animals↗

PubMed1995

Protein that binds to the distal, but not to the proximal, CCAAT of the human thymidine kinase gene promoter.

Mobility shift assays were used to examine protein binding to the human TK gene CCAAT boxes. Similar protein binding patterns were observed with probes containing either the proximal or distal CCAAT. However, probes containing both CCAAT boxes in which one of the CCAAT boxes was inactivated by mutation did not demonstrate identical binding patterns. One of the complexes formed with the longer probes was only observed when the distal CCAAT was intact. This species was not formed with probes that only contained an intact proximal CCAAT, and its formation could only be competed by oligonucleotides containing the distal CCAAT motif. This observation reveals the existence of a protein that can bind to the distal, but not to the proximal, CCAAT of the human TK promoter. This protein may account for the previous observation that the two CCAAT motifs are not functionally equivalent. The protein that binds to the distal, but not to the proximal, CCAAT (DTK-CBP) was also present in two human cell lines. Significantly more DTK-CBP was present in nuclear extracts of HepG2 and WI38 cells than in TK-ts13 cells. However, this protein was not observed in three different murine cell lines and one primary culture. Its abundance in some human cell lines suggests it might modulate the expression of human TK mRNA in cells that express this protein.

3T3 Cells↗